.\"	$OpenBSD: kvm_dump.3,v 1.11 2013/06/05 03:40:26 tedu Exp $
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.Dd $Mdocdate: June 5 2013 $
.Dt KVM_DUMP 3
.Os
.Sh NAME
.Nm kvm_dump_mkheader ,
.Nm kvm_dump_wrtheader ,
.Nm kvm_dump_inval
.Nd crash dump support functions
.Sh SYNOPSIS
.In kvm.h
.Ft int
.Fn kvm_dump_mkheader "kvm_t *kd" "off_t dump_off"
.Ft int
.Fn kvm_dump_wrtheader "kvm_t *kd" "FILE *fp" "int dumpsize"
.Ft int
.Fn kvm_dump_inval "kvm_t *kd"
.Sh DESCRIPTION
First note that the functions described here were designed to be used by
.Xr savecore 8 .
.Pp
The function
.Fn kvm_dump_mkheader
checks if the physical memory file associated with
.Fa kd
contains a valid crash dump header as generated by a dumping kernel.
When a valid header is found,
.Fn kvm_dump_mkheader
initializes the internal kvm data structures as if a crash dump generated by
the
.Xr savecore 8
program was opened.
This has the intentional side effect of enabling the
address translation machinery.
.Pp
A call to
.Fn kvm_dump_mkheader
will most likely be followed by a call to
.Fn kvm_dump_wrtheader .
This function takes care of generating the generic header, the
.Dv CORE_CPU
section and the section header of the
.Dv CORE_DATA
section.
The data is written to the file pointed at by
.Fa fp .
The
.Fa dumpsize
argument is only used to properly set the segment size of the
.Dv CORE_DATA
section.
Note that this function assumes that
.Fa fp
is positioned at file location 0.
This function will not seek and therefore allows
.Fa fp
to be a file pointer obtained by
.Fn zopen .
.Pp
The
.Fn kvm_dump_inval
function clears the magic number in the physical memory file associated with
.Fa kd .
The address translations must be enabled for this to work (thus assuming
that
.Fn kvm_dump_mkheader
was called earlier in the sequence).
.Sh RETURN VALUES
All functions return 0 on success, \-1 on failure.
In the case of failure,
.Xr kvm_geterr 3
can be used to retrieve the cause of the error.
.Sh SEE ALSO
.Xr kvm 3
.Sh HISTORY
These functions first appeared in
.Nx 1.1a .
